Improving health care quality for seniors with diabetes is a critical issue for clinicians, health care systems, and policy-makers. The Medicare STAR program is the primary way in which the Center for Medicare & Medicaid Services (CMS) monitors quality of care for seniors with diabetes in health plans caring for Medicare enrollees. CMS attaches significant monetary incentives to these Medicare STAR measures for health plans, distributing millions of dollars to plans annually based on STAR results. A recent change in CMS policy introduced 3 new diabetes-relevant metrics to the Medicare STAR portfolio in 2012: adherence to oral antihyperglycemic, antihyperlipidemic, and antihypertensive medications. Current guidelines apply these metrics to all Medicare beneficiaries older than 18, with no upper age limit and no adjustment for the number or type of comorbidities patients experience. Quality metrics for patients with chronic illness are generally based on clinical tria evidence of reduced risk for clinical outcomes like cardiovascular events or stroke, and are conducted in younger study populations with few or no comorbidities. These data may not be generalizable or even appropriate for elderly patients, who often have multiple concurrent conditions and who may place a higher value on maintaining quality of life. Whether the CMS-defined adherence measures are sufficiently linked to CVD risk factor control outcomes for elderly diabetes patients, especially those with multiple comorbidities, is unknown. In addition, when applied to complex and elderly patients, quality metrics designed to increase medication adherence may increase adverse outcomes such as hypoglycemia and hypotension that reduce quality of life. The objective of this application is to leverage a secondary data source of over 120,000 diabetes patients over the age of 65 to assess how adherence to diabetes oral medications, statins, and blood pressure medications impact safety and outcomes for Medicare patients with diabetes, and to examine how these effects are influenced by the presence of key comorbidities. The specific aims of this research are to examine the impact of advanced age and specific comorbidities on meeting defined levels of adherence to CVD risk factor medications in diabetes patients; to compare the effectiveness of meeting adherence targets on CVD risk factor control, adverse events, and health care utilization; and to disseminate the study's findings to a wide range of clinical, operational, and policy stakeholders. This study will help lay a strong foundation for developing patient-centered diabetes quality metrics for the nation's growing Medicare population.